1. Field of the invention
The present invention relates to a data recording apparatus and a data reproducing apparatus for respectively recording and reproducing data to and from a recording medium having a sector structure.
2. Description of the Prior Art
When digital signals are recorded to a recording medium such as an optical disk or magnetic disk, the recording tracks are generally divided into plural sectors, and the data is recorded and reproduced by sector unit.
Specifications related to the data disk are regulated, for instance, by ISO/IEC DIS 10090. FIG. 12 shows a block diagram of the conventional reproducing apparatus according to the above regulation and FIGS. 13 and 14 show the sector format and the data format according thereto, respectively.
Each sector includes an ID section and a data section. Each data section contains a resynchronization (RS) mark every 15 bytes, but there are no RS marks or equivalent marks written to the ID section.
A data reproducing apparatus for reproducing signals recorded with this conventional format generally uses a reproducing method as described below. Specifically, the synchronization marks (SB1, SB2, SB3; referred to as "SYNC" hereinbelow) indicating the beginning of the data unit and the RS marks are detected by SYNC detection circuit 41 and RS detection circuit 42, respectively, and the data is read by synchronizing to these detected signals. Some means of interpolation must also be applied when the signals required for synchronization are not correctly detected, however, because the data cannot be reliably read without accurate synchronization. These interpolation methods have typically interpolated the needed synchronization marks based on a previously detected normal signal to output the expected signal at the point where it should have been detected. For example, a missed RS mark is interpolated from the previous RS mark by RS substitution signal generator 44, and SYNC mark is interpolated from the SM detection signal, the detected SYNC signal of the previous sector, or the final RS mark in the data unit of the previous sector by SYNC substitution signal generator 43.
However, when there is a significant time lag between the previously detected signal and the interpolated signal, implementing the above method necessitates a trade-off between the use of large-scale, complex circuitry or a drop in data reliability.